[Frank Lee]

The scuff looks only cosmetic- no problem. If the cut is as shallow as you say it probably won't be a problem- at least in the short term- but eventually it could hasten the decomposition of the cords. I've never tried it but I've thought of gooping silicone caulk into such cuts and cracks. The real problem is what we don't see but you have said- the tire being driven flat for ten miles. I would expect internal damage from that. Make sure the spare is good and inflated.

Tires are an expensive up-front purchase but when you think of them in terms of cents/mile, it can pay to simply get good ones vs messing around with junk... and this is from someone who does in fact run junkyard tires and extract the very last mile out of them. It depends on how willing you are to mount the spare at roadside and otherwise deal with them.

If you are going to run a structurally compromised tire I think it's best to put it on the rear- especially with fwd cars- and not inflate above sidewall max pressure, or maybe even the automaker's recommended pressure. The rear is more lightly loaded from static and dynamic forces and if it has balance and smoothness issues they are less annoying out back.